Top Course
Top Course
Product Description
Crushed Surfacing Top Course (CSTC) is a 5/8″ minus gravel product. It’s a state-spec crushed rock product that contains fines, which allow it to pack down tightly and stay in place when compressed.
CSTC is manufactured at Kapowsin Quarry from quarried basalt rock. It is fractured and angular.
CSTC meets WSDOT Standard Specifications 9-03.9(3) for grading:
- 99–100% passing the ¾” screen
- 80–100% passing the ½” screen
- 46–66% passing the #4 screen
- 8–24% passing the #40 screen
- up to 10% passing the #200 screen
Our CSTC also meets or exceeds all quality test requirements for fracturing, sand equivalency, abrasion, and degradation.
Product Applications
Like the name suggests, top course is typically used as a top layer on gravel driveways and parking lots. It’s often placed on top of Crushed Surfacing Base Course (CSBC).
CSTC can be used on its own to build driveways used by light cars or equipment. More often, it’s used in combination with CSBC to create sturdier roads.
Similar Products
CSBC (1¼” Minus) is often used as a base material on top of which CSTC is spread. CSBC can also be used on its own on roads used by heavy equipment.
Variations of CSTC include ¾” Shoulder Rock and Maintenance Rock.
Helpful Tips
If you’re stumped about whether to use clean or minus material, check out our “Clean v. Minus” guide.
You can also refer to our popular article and video, “Choosing the Right Rock: Comparing Crushed Rock Sizes and Types.”
About Top Course
Top Course refers to a top layer of material that works with a base course to create sturdy driving or paving surfaces. It’s also referred to as “surface course” or “keystone.” Washington Rock’s top course is a 5/8″ minus product that is made to a specification dictated by the Washington State Department of Transportation (WSDOT).
Pricing & Availability
Minimum $35.00 purchase required on all materials. Check pricing and availability by requesting a quote online.
Material Spreading
Prices quoted are for material delivery only. Drivers do their best to dump material evenly when requested. However, Washington Rock cannot guarantee that this will result in an even or desirable distribution of material. Customers must supply the equipment and labor necessary to finish projects.
Minimum Delivery Quantity
Our minimum order quantity for deliveries is 10 cubic yards. Do you need less than that? Find a local supplier here.